**1. Introduction**

Sugarcane is a major contributor to world sugar and more than 70% of global saccharine needs are fulfilled by this sweet grass. It has been cultivated since pre-historic times as a sugar source. Further, it has great potential to be used for the production of bioethanol and has been grown in many countries as an energy crop. Brazil is the top most consumer of sugarcane biofuel followed by USA and fulfill 50% of their energy needs through biofuel. They run more than 5.0 million automobiles on hydrous ethanol at an ethanol content of 95.5% [1]. These facts direct us to strive for the improvement of sugarcane crop so that global energy needs may be fulfilled

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sustainably. Various promising varieties have been developed so far but they are posed to certain drastic stresses including biotic as well as abiotic stresses. Similarly, efforts have been made to improve sugar recovery. Since, crop productivity and quality can only be improved by employing innovative technologies. Plant tissue culture and genetic engineering has great potential to resolve problems faced by this crop [2]. Transgenic technology can do a lot to address all the aforementioned yield limiting constraints as any of the alien genes may be introduced into the plant through genetic transformation methodologies. Different methods of transformation i.e. biolistic [3, 4] *Agrobacterium* [5] and electroporation [6] have been employed to engineer valuable agronomic traits like resistance against weedicides [7], viruses [8] and insects [3]. Efforts have been made to engineer metabolic pathways for improved sugar content [9] and for the production of biopolymers and bioplastics. Omics approaches have contributed a lot to understand and explore sugarcane genome to develop improved clones. Milestones in structural and functional genomics are also convincing. Different types of markers have been developed to speed up molecular breeding through early identification of superior genotypes [10]. Thus, biotechnological interventions have great potential to promote sugarcane not only as future energy crop but also a factory house for the production of therapeutics and industrial compounds.

in metabolic pathways and sucrose accumulation will prove a real milestone in developing future energy crop. Similarly, importance of *in vitro* techniques have been highlighted that how advancements in tissue culture techniques are important for germplasm conservation, development of somaclonal variants and genetic transformation. Likewise, potential of transgenic technology has been discussed to develop insect resistant, disease resistant and herbicide tolerant plants. Omics, a real potential area of future research, has been overviewed to highlight the role of genomics, transcriptomics, proteomics and metabolomics in sugarcane

Biotechnological Interventions for the Improvement of Sugarcane Crop and Sugar Production

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**2. Tissue culture based approaches for sugarcane crop improvement**

Since the pioneer work on callus induction at Hawaiian Sugar Planters' Association Experiment Station and the method developed by Nickell [11] for root production, sugarcane tissue culture appeared as a valuable tool for diverse research activities. Shortly after this, Heinz and Mee [12] published the first report on sugarcane regeneration. These *in vitro* techniques had huge impact on basic research and also on the research of commercial interest which includes maintenance of elite germplasm, production of agronomically superior somaclones, micropropagation of elite clones, healthy planting material and screening for abiotic/biotic stress

Somatic embryogenesis may be divided into two phases: induction and expression. During the induction phase, embryogenic competence is acquired by differentiated somatic cells whereas during expression phase, embryogenic cells differentiate into somatic embryos. Komamine et al. [13] evaluated that embryogenic cells did not require any exogenous stimuli in the form of growth hormones or vitamins at induction state. Rather, competent cells require exogenous stimuli at transitional state in very minute quantities. Somatic embryogenesis may either be direct or indirect. Direct somatic embryogenesis involves development of embryo directly on the surface of explant tissues i.e. stem segments, leaf segments, young inflorescence, zygotic embryo, protoplasts and microspores. Indirect somatic embryogenesis involves an intermediary step of callus induction followed by embryogenesis. Different factors have been found to play key role in the acquisition of embryogenic competence. Exogenous growth regulators promote embryogenic competence by affecting cell polarity, pH gradients and by modifying ionic balance all around the cells. Intracellular pH is very crucial for embryogenic competence acquisition. Another critical aspect is the physical isolation of a cell from others. Embryogenic competence acquisition by somatic cells is regulated by the expression of certain genes which involve either upregulation or down regulation of certain functional genes. In addition, physiological, morphological and metabolic variations are also very important for the acquisition of embryogenic competence. Thus, somatic embryogenesis is a great milestone in sugarcane biotechnology [14]. Originally this method was developed as a substitute of meristem culture and regeneration but now it has become an important component of genetic engineering as well. It has well been exploited for the preservation of mutants and transformed material till

crop improvement and in developing energy cane (**Figure 1**).

tolerance.

**2.1. Somatic embryogenesis**

These interventions have been discussed here to focus critical areas of research that can attract researchers for the improvement of this crop. Understanding molecular mechanisms involved

**Figure 1.** Schematic sketch showing role of biotechnological interventions for the improvement of sugarcane crop and sugar production.

in metabolic pathways and sucrose accumulation will prove a real milestone in developing future energy crop. Similarly, importance of *in vitro* techniques have been highlighted that how advancements in tissue culture techniques are important for germplasm conservation, development of somaclonal variants and genetic transformation. Likewise, potential of transgenic technology has been discussed to develop insect resistant, disease resistant and herbicide tolerant plants. Omics, a real potential area of future research, has been overviewed to highlight the role of genomics, transcriptomics, proteomics and metabolomics in sugarcane crop improvement and in developing energy cane (**Figure 1**).
